Since fingerprint patterns of ridge endings and ridge bifurcations do not vary with time for an individual and the pattern on each finger for any individual is unique and differentiates that individual from the rest of society, fingerprint comparison is an absolute means of identification. This fact has been accepted by the scientific community and by the courts. Fingerprint identification is legally recognized forensic evidence of an individual's presence at a scene or association with property or instruments used in a crime. Fingerprint identification is also used commercially such as on identification cards for security systems, check identification means, and in many non-criminal government agencies. Fingerprint identification is coming into use as a means of identifying and locating missing children and foot-print identification is in almost universal usage in developed countries for infant identification.
Any reliable fingerprint identification system requires imaging a distinct print pattern on a substrate. Even in commercial identification systems such as with checks, it is important that the system be inoffensive to the subject. The early inking systems were based on greasy black inks. These systems were difficult to utilize since it required much skill, training and care to provide a distinct print without ink running between ridges and obliterating substantial areas of the print image. Furthermore, the inking system was messy to use for both the operator and the subject, requiring towelettes or a trip to a wash basin in order to remove the ink.